Solar Probe, a mission with a long pedigree

[Jim]

Not required, if that were the case.  NASA doesn't have do such a thing if a launch vehicle on the NLS II meets the requirements.

I will defer to your greater knowledge (I did say I was being sarcastic...).

Having adjusted the creases on my tinfoil hat, it could be that NASA is anticipating non-availability of the Atlas V & is preemptively looking for a potential replacement launcher (Falcon Heavy, Ariane V, what have you...).

Neither have the capability and NASA can't buy an Ariane

[GClark]

Again, as you say...

Which still begs the question, why is NASA doing this?  What's going on?

[ugordan]

I'll ask the question again: is this basically fishing for a Delta IV Heavy as it's the only other eligible booster with performance required, but not available via NLS-II?

If so, does it mean the Atlas 551 + Star 48B combo doesn't have enough performance margin? Atlas manifest issues? Perhaps NASA thinks a D-IV would actually be cheaper in this instance?

Or, is it one of those contractual twists where only a vanilla Atlas with no kick stage is available to be directly purchased so it has to be handled this way?

[Jim]

Again, as you say...

Which still begs the question, why is NASA doing this?  What's going on?

I thought I posted a response but must not have hit post.  I was going to say that you overlooked a launch vehicle.

[Jim]

Or, is it one of those contractual twists where only a vanilla Atlas with no kick stage is available to be directly purchased so it has to be handled this way?

The way around that is to have the spacecraft be responsible for the kick stage or purchase it separately.

I missed your comment on the other page.   It needs more performance than what is available of existing contracts

[vapour_nudge]

I thought I posted a response but must not have hit post.  I was going to say that you overlooked a launch vehicle.

SLS?

[ugordan]

I thought I posted a response but must not have hit post.  I was going to say that you overlooked a launch vehicle.

SLS?

Did you even read the solicitation?

Potential offerors shall have had at least one successful flight of the common launch vehicle configuration, as defined in NASA Policy Directive (NPD) 8610.7D Launch Services Risk Mitigation Policy for NASA-Owned and/or NASA-Sponsored Payloads/Missions prior to the proposal due date, which is anticipated to be September 2014.

Bold mine.

[vapour_nudge]

Nope.

[arachnitect]

I find, so I share:

https://dnnpro.outer.jhuapl.edu/Portals/35/ISSFD24_Paper_Release/ISSFD24_Paper_S6-2_Guo.pdf

The launch energy is much higher than most interplanetary missions and requires a powerful three-stage launch system. The maximum launch C3 over the 20-day launch period is 154 km2/s2. The baseline launch system is an EELV (Evolved Expendable Launch Vehicle) Delta IV Heavy class launch vehicle with a standard Star 48 BV upper stage. During the Phase B development, an EELV Atlas V 551 launch vehicle was assumed. The recent switch to the more powerful Delta IV Heavy class launch vehicle will allow for more launch mass and increase spacecraft mass margin for the Phase C development.

They were playing around with an enhanced Star-48 at one point (trying to keep it on Atlas).

[Proponent]

I find, so I share:

https://dnnpro.outer.jhuapl.edu/Portals/35/ISSFD24_Paper_Release/ISSFD24_Paper_S6-2_Guo.pdf

Would anyone have a copy or functioning link for the above paper?

I'll add a 1961 paper that I recently found on NTRS.  It's the earliest reference I am aware of to a solar probe.

EDIT:  Corrected quoting.

[speedevil]

Here are some images of the current configuration of Solar Probe Plus.

The previous designs got a _lot_ hotter, as closer to the sun.